1. Field of the Invention
One or more embodiments of the present invention generally relate to an apparatus and method for enhancing graphics generated by a graphics processor unit (“GPU”), and more particularly, to an apparatus and method for converting the format of computer-generated images.
2. Description of the Related Art
With the introduction of the graphics processor unit (“GPU”), computationally intensive calculations for generating graphics, which were traditionally performed by a central processing unit (“CPU”), have been offloaded to the GPU. The GPU has enabled computer workstations to become more integrated in generating sophisticated digital content creation and performing other video processing tasks, including editing (e.g., nonlinear editing) and creating special effects for video images.
Media creators, such as film makers, photographers, television broadcasters, and even medical imaging professionals often require that GPU-generated graphics and ancillary video signals be produced and transported at a high definition resolution. “High definition” typically refers to images having a resolution such as 1920 horizontal pixels by 1080 vertical pixels, regardless if interlaced or progressively scanned. To integrate graphics into real-time video broadcasts and/or and post-production video processing, these creators of content are using various converters and devices, such as serial digital interface (“SDI”) converters, to generate video images at high-definition resolutions from GPU-generated images.
An SDI converter is a device for converting computer-generated images into uncompressed standard-definition SDI and high-definition SDI video formats. An SDI converter generally provides for improved HD imaging over traditional scan converters by receiving 8-bit color components via a high-speed serial interface especially designed to transport pixel data over channels connecting the SDI converter to the GPU. Each channel typically includes three data channels for transporting 8 bits of the red component over a first data channel, 8 bits of the green component over a second data channel, and 8 bits of the blue component over the third data channel, thereby providing 24 bits of pixel data in RGB color space format.
Digital Visual Interface (“DVI”) is an example of such a high-speed interface. A DVI is designed to transport pixel data using transition minimized differential signaling (“TMDS”), which encodes each 8-bit color component into a 10-bit transition minimized signal, adding two bits of control information. By using TMDS, each DVI channel enables their three, 8-bit data channels to provide the RGB information currently at a bandwidth of 165 MHz. Generally, the fundamental principles of TMDS are well-known and need not be discussed in detail.
One drawback to this approach is that the throughput of bits is generally limited to 8-bits per data channel and/or one color component (i.e., R, G, or B) per data channel. This, in turn, limits the amount and the form in which pixel data can be transported during a given time interval. Another drawback to this implementation is that when generating HD video, SDI formatting typically requires that each 8-bit RGB color component be converted to, for example, a 10-bit YCrCb color component. Without the increased resolution provided by the additional 2 bits of the YCrCb color space format, the video generated at the SD/HD-SDI output by the SDI converter is suboptimal. That is, a video generated by the SDI converter lacks the resolution to smooth the graduations of colors, such as from a dark-colored background to a lighter-colored background, to avoid producing a perceptible color banding or a set of “stair-stepped” contour lines betweens the graduations of colors.
Therefore, a need exists in the art for an improved method and apparatus for converting computer-generated images into uncompressed standard-definition SDI and high-definition SDI video formats.